Intervertebral prosthetic device for spinal stabilization and method of implanting same

ABSTRACT

A prosthetic device and method, according to which a member of a relatively flexible, soft material is connected with a member of a relatively stiff material and the connected members are implanted in a spinal column using a non-rigid and a rigid connection.

BACKGROUND

The present invention relates to an intervertebral prosthetic device forstabilizing the human spine, and a method of implanting same. Spinaldiscs that extend between adjacent vertebrae in vertebral columns of thehuman body provide critical support between the adjacent vertebrae whilepermitting multiple degrees of motion.

These discs can rupture, degenerate, and/or protrude by injury,degradation, disease, or the like to such a degree that theintervertebral space between adjacent vertebrae collapses as the discloses at least a part of its support function, which can causeimpingement of the nerve roots and severe pain.

In these cases, intervertebral prosthetic devices have been designedthat can be implanted between the adjacent vertebrae, both anterior andposterior of the column and are supported by the respective spinousprocesses of the vertebrae to prevent the collapse of the intervertebralspace between the adjacent vertebrae and provide motion stabilization ofthe spine. Many of these devices are supported between the spinousprocesses of the adjacent vertebrae.

In some situations it is often necessary to remove the laminae and thespinous process from at least one of the adjacent vertebrae to getproper decompression. In other situations, the defective disc is removedand two vertebral segments are fused together to stop any motion betweenthe segments and thus relieve the pain. When two adjacent vertebrae arefused, the laminae and the spinous process of at least one vertebrae areno longer needed and are therefore often removed.

However, in both of the above situations involving removal of a spinousprocess, it would be impossible to implant an intervertebral prostheticdevice of the above type since the device requires support from bothprocesses.

SUMMARY

According to an embodiment of the invention, an intervertebralprosthetic device is provided that is implantable between two adjacentvertebrae, at least one of which is void of a spinous process, toprovide motion stabilization.

Various embodiments of the invention may possess one or more of theabove features and advantages, or provide one or more solutions to theabove problems existing in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an adult human vertebral column.

FIG. 2 is a posterior elevational view of the column of FIG. 1.

FIG. 3 is an enlarged, front elevational view of one of the vertebrae ofthe column of FIGS. 1 and 2.

FIG. 4 is an enlarged, partial, isometric view of a portion of thecolumn of FIGS. 1 and 2, including the lower three vertebrae of thecolumn, and depicting intervertebral prosthetic device according to anembodiment of the invention implanted between two adjacent vertebrae.

FIG. 5 is an enlarged, isometric, exploded view of the prosthetic deviceof FIG. 4.

FIG. 6 is a cross-sectional view of the implanted device of FIGS. 4 and5.

FIG. 7 is an enlarged, isometric, exploded view of an alternateembodiment of the prosthetic device of FIG. 5.

DETAILED DESCRIPTION

With reference to FIGS. 1 and 2, the reference numeral 10 refers, ingeneral, to a human vertebral column 10. The lower portion of thevertebral column 10 is shown and includes the lumbar region 12, thevertebrae V6, and the coccyx 16. The flexible, soft portion of thevertebral column 10, which includes the thoracic region and the cervicalregion, is not shown.

The lumbar region 12 of the vertebral column 10 includes five vertebraeV1, V2, V3, V4 and V5 separated by intervertebral discs D1, D2, D3, andD4, with the disc D1 extending between the vertebrae V1 and V2, the discD2 extending between the. vertebrae V2 and V3, the disc D3 extendingbetween the vertebrae V3 and V4, and the disc D4 extending between thevertebrae V4 and V5.

The vertebrae V6 includes five fused vertebrae, one of which is asuperior vertebrae V6 separated from the vertebrae V5 by a disc D5. Theother four fused vertebrae of the sacrum 14 are referred to collectivelyas V7. A disc D6 separates the vertebrae V6 from the coccyx 16 whichincludes four fused vertebrae (not referenced).

With reference to FIG. 3, the vertebrae V5 includes two laminae 20 a and20 b extending to either side (as viewed in FIG. 2) of a spinous process22 that projects posteriorly from the juncture of the two laminae. Twotransverse processes 24 a and 24 b extend laterally from the laminae 20a and 20 b, respectively, and two pedicles 26 a and 26 b extendinferiorly from the processes 24 a and 24 b to a vertebral body 28.Since the other vertebrae V1-V3 are similar to the vertebrae V5 theywill not be described in detail. Also, V4 is similar to V5 with theexception that the spinous process 22 of V4 has been removed for one orboth of the reasons set forth below.

Referring to FIG. 4, it will be assumed that, for one or more of thereasons set forth above, the vertebrae V4 and V5 are not beingadequately supported by the disc D4 and that it is therefore necessaryto provide supplemental support and stabilization of these vertebrae. Asstated above, it will also be assumed that the spinous process 22 of V4has been removed.

An intervertebral disc prosthetic device 40 according to an embodimentof the invention is provided which is adapted to be implanted betweenthe spinous processes 22 of the vertebrae V3 and V5. The prostheticdevice 40 is shown in detail in FIGS. 5 and 6 and includes a spacer 42which is substantially rectangular in shape with the exception that twocurved notches 42 a and 42 b are formed its respective end portions. Alaterally extending channel 42 c, having a substantially rectangularcross section, extends through the entire width of the spacer 42approximately midway between the notches 42 a and 42 b.

An insert 44 is provided that is dimensioned so as to extend in thechannel 42 c with minimum clearance. Tabs 46 a and 46 b extend out fromthe respective ends of the insert 44 and elongated openings 46 c and 46d extend through the respective tabs. The length of the insert 44substantially corresponds to the length of the channel 42 c so that whenthe insert is inserted in the channel, the tabs 46 a and 46 b projectoutwardly from the channel.

Two protrusions 48 a and 48 b extend from the sides of the tab 46 a andtwo protrusions 48 c and 48 d extend from the sides of the tab 46 b. Theprotrusions are for the purpose of receiving tethers, or the like, totether the device 40 to the vertebrae V4 and/or V5.

Since the spinous process of the vertebrae V4 has been removed, thedevice 40 is implanted between the spinous process 22 of the vertebraeV3 and the spinous process 22 of the vertebrae V5. In the implantedposition shown in FIGS. 4 and 6, the spinous process 22 of the vertebraeV3 extends in the notch 42 a of the spacer 42, and the spinous process22 of the vertebrae V5 extends in the notch 42 b. The dimensions of thedevice 40 are such that, when it is implanted in this manner, theelongated openings 46 c and 46 d extend over the pedicles 26 a and 26 b(FIG. 3) of the vertebrae V4.

Then, two screws, one of which is referred to by the reference numeral49 in FIGS. 4 and 6, are inserted through the elongated openings 42 cand 42 d, respectively, of the spacer 42. Torque is applied to thescrews 49 so that they are driven into the pedicles 26 a and 26 b of thevertebrae V4. The elongated openings 46 c and 46 d in the tabs 46 a and46 b, respectively, enable the screws 49 to be adjusted laterally and tobe angled towards the pedicles 26 a and 26 b as necessary so that theycan be driven into the pedicles.

Although not shown in the drawing, tethers can be tied between theprotrusions 46 a-46 d and the vertebrae V3, V4, and/or V5 to provideadditional support and resistance.

As examples of the materials making up the spacer 42 and the insert 44,the spacer can be of a relatively soft material, such as soft plastic,including silicone, while the insert can be of a relatively stiffmaterial, such as hard plastic or rubber. In the latter context, thesurgeon could be provided with several inserts 44 that vary instiffness, and once the condition of the vertebrae V4 and V5 (FIG. 4),and therefore the desired stiffness, is determined, the proper insert 44can be selected.

When the device 40 is implanted in the manner discussed above, therelatively flexible, soft spacer 42 provides non-rigid connections tothe vertebrae V3 and V5 that readily conforms to the processes 22 of thevertebrae V3 and V5 and provides excellent shock absorption, while theinsert 44 adds stiffness, compressive strength and durability, and thescrews 49 provide a rigid connection to the vertebrae V4.

A prosthetic device 50 according to another embodiment is shown indetail in FIG. 7 and includes a spacer 52 which is substantiallyrectangular in shape with the exception that a curved notch 52 a, isformed in one end portion. A tab 52 b projects from the other end of thespacer 52 for reasons to be described.

A spacer 54 is also provided which is substantially rectangular in shapewith the exception that a curved notch 54 a is formed in one end portionand a tab 54 projects from the other end of the spacer 52.

A connector 56 is designed to fit over the tabs 52 b and 54 b of thespacers 52 and 54, respectively, to connect them. To this end, theconnector 56 has a through opening 56 a with a cross section slightlygreater than the cross sections of the tabs 52 b and 54 b.

Two tabs 56 b and 56 b extend out from the respective ends of theconnector 56, and elongated openings 56 c and 56 d extend through therespective tabs for receiving screws, for reasons to be described.

Two protrusions 58 a and 58 b extend from the sides of the tab 56 b andtwo protrusions 58 c and 58 d extend from the sides of the tab 56 c. Theprotrusions are for the purpose of receiving tethers, or the like, totether the device 40 to the vertebrae V4 and/or V5.

To connect the spacers 52 and 54, their respective tabs 52 b and 54 bare inserted into the opening 56 a of the connector 56 from oppositeends of the opening until the corresponding shoulders of the spacers 52and 54 engage the corresponding ends of the connector 56. The spacers 52and 54 and the connector are sized so that the tabs 52 a and 54 a engagethe inner wall of the connector 56 in a friction fit so as to retain thespacers 52 and 54 in the connector.

Since the spinous process of the vertebrae V4 has been removed, thedevice 50 is implanted between the spinous process 22 of the vertebraeV3 and the spinous process 22 of the vertebrae V5. In the implantedposition, the spinous process 22 of the vertebrae V3 extends in thenotch 52 a of the spacer 42, and the spinous process 22 of the vertebraeV5 extends in the notch 52 b. The dimensions of the device 50 are suchthat, when it is implanted in this manner, the elongated openings 56 cand 56 d extend over the pedicles 26 a and 26 b (FIG. 3) of thevertebrae V4.

Although not shown in the drawing, tethers can be tied between theprotrusions 58 a-58 d and the vertebrae V3, V4, and/or V5 to provideadditional support and resistance.

The spacers 52 and 54 could be fabricated from a relatively softmaterial, such as soft plastic, including silicone, while the connector56 could be fabricated from a relatively stiff material, such as hardplastic or rubber. In the latter context, the surgeon could be providedwith several connectors 56 that vary in stiffness. Thus, once thesurgeon ascertains the condition of the vertebrae V3, V4, and V5 (FIG.3) and determines the particular stiffness that is needed, the properconnector 56 can be selected.

Thus, when the device 50 is implanted between the processes 22 of thevertebrae V3 and V5 in the manner discussed above, the relativelyflexible, soft spacers 52 and 54 provide a non-rigid connection to thevertebrae V3 and V5 that readily conforms to the processes 22 of thevertebrae V3 and V5, and provides excellent shock absorption. Also, theconnector 56 adds stiffness, compressive strength and durability, andthe screws 49 provide a rigid connection to the vertebrae V4.

It is understood that other variations may be made in the foregoingwithout departing from the invention and examples of some variations areas follows:

-   Any conventional substance that promotes bone growth, such as HA    coating, BMP, or the like, can be incorporated in the prosthetic    device of the above embodiments.-   One or more of the components of the above devices may have through    holes formed therein to improve integration of the bone growth.-   The surfaces of the body member defining the notch can be treated,    such as by providing teeth, ridges, knurling, etc., to better grip    the spinous processes and the adapters.-   The body member can be fabricated of a permanently deformable    material thus providing a clamping action against the spinous    process.-   The spacers and associated components of one or more of the above    embodiments may vary in shape, size, composition, and physical    properties.-   Through openings can be provided through one or more components of    each of the above prosthetic devices to receive tethers for    attaching the devices to a vertebrae or to a spinous process.-   The prosthetic device of each of the above embodiments can be placed    between two vertebrae in the vertebral column 10 other than the ones    described above.-   The prosthetic device of each of the above embodiments can be    fabricated from materials other than those described above.-   The relative stiff components described above could be made of a    resorbable material so that their stiffness would change over time.-   The prosthesis of the above embodiments can be implanted between    body portions other than vertebrae.-   In the embodiment of FIG. 7, the spacers 52 and 54 can be fabricated    from a relatively stiff material and the connector 56 from a    relatively soft, flexible material.-   The prostheses of the above embodiments can be inserted between two    vertebrae following a discectemy in which a disc between the    adjacent vertebrae is removed, or a corpectomy in which at least one    vertebrae is removed.-   The spatial references made above, such as “under”, “over”,    “between”, “flexible, soft”, “lower”, “top”, “bottom”, etc. are for    the purpose of illustration only and do not limit the specific    orientation or location of the structure described above.

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, therefore, that other expedientsknown to those skilled in the art or disclosed herein, may be employedwithout departing from the invention or the scope of the appendedclaims, as detailed above. In the claims, means-plus-function clausesare intended to cover the structures described herein as performing therecited function and not only structural equivalents but also equivalentstructures. Thus, although a nail and a screw may not be structuralequivalents in that a nail employs a cylindrical surface to securewooden parts together, whereas a screw employs a helical surface, in theenvironment of fastening wooden parts a nail and a screw are equivalentstructures.

1. A prosthetic device for insertion in a spinal column, the devicecomprising: a first member of a relatively flexible material; a secondmember of a relatively stiff material connected to the first member;means for providing a non-rigid connection of one of the members to avertebrae of the column; and means for providing a rigid connection ofone of the members to a vertebrae of the column.
 2. The device of claim1 wherein the second member is supported by the first member.
 3. Thedevice of claim 2 wherein the first member is a spacer and the secondmember is an insert that extends in a channel formed in the spacer. 4.The device of claim 3 wherein the means for providing the non-rigidconnection comprises two notches formed in the spacer for engaging therespective spinous processes of two vertebrae.
 5. The device of claim 1wherein the spinous process of one vertebrae of the column is removedand wherein the notches engage the respective spinous processes of thevertebrae adjacent the one vertebrae.
 6. The device of claim 3 whereinthe means for providing the rigid connection comprises two screwsextending through an opening in the spacer and into the pedicles of avertebrae.
 7. The device of claim 1 wherein the second member has anopening for receiving a tab on the first member to connect the members.8. The device of claim 7 further comprising a third member having a tabthat also extends in the opening of the second member.
 9. The device ofclaim 8 wherein the means for providing the non-rigid connectioncomprises a notch formed in the first member and in the third member forengaging the respective spinous processes of two vertebrae.
 10. Thedevice of claim 9 wherein the spinous process of one vertebrae of thecolumn is removed and wherein the notches engage the respective spinousprocesses of the vertebrae adjacent the one vertebrae.
 11. The device ofclaim 10 wherein the means for providing the rigid connection comprisestwo screws extending openings in the second member and into the pediclesof the one vertebrae.
 12. The device of claim 1 further comprising meanson one of the members for receiving a cable to tether the latter memberto a vertebrae of the column.
 13. A method of implanting a prostheticdevice in a spinal column to stabilize the spine, the method comprising:connecting a first member of a relatively flexible material to a secondmember of a relatively stiff material; establishing a non-rigidconnection between one of the members and a vertebrae; and establishinga rigid connection between one of the members and a vertebrae of thespinal column.
 14. The method of claim 13 wherein the first-mentionedstep of connecting comprises supporting the second member by the firstmember.
 15. The method of claim 14 wherein the first-mentioned step ofconnecting further comprises supporting the second member in a channelin the first member.
 16. The method of claim 13 wherein the step ofestablishing the non-rigid connection comprises forming two notches inthe one member for engaging the respective spinous processes of twovertebrae.
 17. The method of claim 16 wherein the spinous process of onevertebrae of the column is removed and wherein the notches engage therespective spinous processes of the vertebrae adjacent the onevertebrae.
 18. The method of claim 17 wherein the step of establishingthe rigid connection comprises inserting at least one screw through acorresponding opening in one of the members and into the correspondingpedicle of the one vertebrae.
 19. The method of claim 13 wherein thestep of establishing the rigid connection comprises inserting at leastone screw through a corresponding opening in one of the members and intothe corresponding pedicle of the vertebrae.
 20. The method of claim 13wherein the first-mentioned step of connecting comprises inserting a tabon one of the members into an opening in the other member.
 21. Themethod of claim 20 further comprising inserting a tab on a third memberinto the opening.
 22. The method of claim 21 wherein the step ofestablishing the non-rigid connection comprises forming a notch in theone member and in the third member for engaging the respective spinousprocesses of the vertebrae.
 23. The method of claim 22 wherein thespinous process of one vertebrae of the column is removed and whereinthe notches engage the respective spinous processes of the vertebraeadjacent the one vertebrae.
 24. The method of claim 23 wherein the stepof establishing the rigid connection comprises two screws extendingthrough openings in the one member and into the respective pedicles ofthe one vertebrae.
 25. The method of claim 13 wherein the step ofestablishing the rigid connection comprises at least one screw extendingthrough an opening in the one member and into a pedicle of thevertebrae.
 26. The method of claim 13 further comprising tethering oneof the members to a vertebrae of the column.